U.S. patent application number 13/425268 was filed with the patent office on 2013-09-19 for explicit indication of uplink control channel resources in carrier aggregation systems.
The applicant listed for this patent is Mark Andrew Earnshaw, Jun Li, Yiping Wang. Invention is credited to Mark Andrew Earnshaw, Jun Li, Yiping Wang.
Application Number | 20130242881 13/425268 |
Document ID | / |
Family ID | 49157545 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130242881 |
Kind Code |
A1 |
Wang; Yiping ; et
al. |
September 19, 2013 |
EXPLICIT INDICATION OF UPLINK CONTROL CHANNEL RESOURCES IN CARRIER
AGGREGATION SYSTEMS
Abstract
Systems, apparatuses, and methods performed as part of a
wireless communications network include determining a downlink (DL)
hybrid automatic repeat request (HARQ) timing for a first component
carrier and a second component carrier, the first component carrier
having a different DL HARQ timing configuration than the second
component carrier. A physical uplink control channel (PUCCH)
resource can be identified for the second component carrier. An
indicator of the PUCCH resource can be sent to a user
equipment.
Inventors: |
Wang; Yiping; (Allen,
TX) ; Earnshaw; Mark Andrew; (Kanata, CA) ;
Li; Jun; (Richardson, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wang; Yiping
Earnshaw; Mark Andrew
Li; Jun |
Allen
Kanata
Richardson |
TX
TX |
US
CA
US |
|
|
Family ID: |
49157545 |
Appl. No.: |
13/425268 |
Filed: |
March 20, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61612132 |
Mar 16, 2012 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 5/0094 20130101;
H04L 5/0055 20130101; H04L 5/0023 20130101; H04L 5/001 20130101;
H04L 5/1469 20130101; H04L 1/18 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20090101
H04W072/04 |
Claims
1. A method performed in a base station of a wireless
communications network, the method comprising: determining downlink
(DL) hybrid automatic repeat request (HARQ) timing linkages for a
first component carrier and a second component carrier, the first
component carrier having a different DL HARQ timing configuration
than the second component carrier; identifying a physical uplink
control channel (PUCCH) resource for the second component carrier;
and sending an indicator of the PUCCH resource to a user
equipment.
2. The method of claim 1, wherein the PUCCH resource is indicated
based, at least in part, on at least one acknowledgement/negative
acknowledgement resource indicator (ARI) bit.
3. The method of claim 2, wherein the at least one ARI bit is
communicated with at least one transmit power control (TPC)
bit.
4. The method of claim 1, wherein the first component carrier
comprises a primary cell and the second component carrier comprises
a secondary cell.
5. A network element for a wireless communications system, the
network element comprising: a processor operable to execute
instructions comprising: determining downlink (DL) hybrid automatic
repeat request (HARQ) timing linkages for a first component carrier
and a second component carrier, the first component carrier having
a different DL HARQ timing configuration than the second component
carrier; identifying a physical uplink control channel (PUCCH)
resource for the second component carrier; and sending an indicator
of the PUCCH resource to a user equipment.
6. The network element of claim 5, wherein the PUCCH resource is
indicated based, at least in part, on at least one
acknowledgement/negative acknowledgement resource indicator (ARI)
bit.
7. The network element of claim 6, wherein the at least one ARI bit
is communicated with at least one transmit power control (TPC)
bit.
8. The network element of claim 5, wherein the first component
carrier comprises a primary cell and the second component carrier
comprises a secondary cell.
9. A method for a user equipment for a wireless communications
network, the method comprising: receiving an indicator from a base
station, the indicator indicating a physical uplink control channel
(PUCCH) resource identification for a component carrier; and using
the indicator received from the base station to identify the PUCCH
resource for the component carrier.
10. The method of claim 9, wherein the UE has a first component
carrier and a second component carrier, and the indicator
identifies the PUCCH resource for the second component carrier.
11. The method of claim 9, wherein the first component carrier
controls power for the second component carrier, and the indicator
is based on at least one transmit power control (TPC) bit for the
second component carrier.
12. A user equipment (UE) for a wireless communications network,
the UE comprising: a processor operable to execute instructions
comprising: receiving an indicator from a base station, the
indicator indicating a physical uplink control channel (PUCCH)
resource identification for a component carrier; and using the
indicator received from the base station to identify the PUCCH
resource for the component carrier.
13. The UE of claim 12, wherein the UE has a first component
carrier and a second component carrier, and the indicator
identifies the PUCCH resource for the second component carrier.
14. The UE of claim 12, wherein the first component carrier
controls power for the second component carrier, and the indicator
is based on at least one transmit power control (TPC) bit for the
second component carrier.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/612,132
filed Mar. 16, 2012.
FIELD
[0002] The present disclosure pertains to uplink control channel
resource collisions, and more particularly to physical uplink
control channel resource collisions that may occur in systems using
in inter-band carrier aggregation with different TDD UL/DL
configurations.
BACKGROUND
[0003] In wireless communications systems, such as long term
evolution (LTE) systems, downlink and uplink transmissions may be
organized into two duplex modes: frequency division duplex (FDD)
mode and time division duplex (TDD) mode. The FDD mode uses a
paired spectrum where the frequency domain is used to separate the
uplink (UL) and downlink (DL) transmissions. FIG. 1A is a graphical
illustration of an uplink and downlink subframe separated in the
frequency domain for the FDD mode. In TDD systems, an unpaired
spectrum may be used where both UL and DL are transmitted over the
same carrier frequency. The UL and DL are separated in the time
domain. FIG. 1B is a graphical illustration of uplink and downlink
subframes sharing a carrier frequency in the TDD mode. In
LTE-Advanced, carrier aggregation allows expansion of effective
bandwidth delivered to a user terminal through concurrent
utilization of radio resources across multiple carriers. Multiple
component carriers are aggregated to form a larger overall
transmission bandwidth. Carrier aggregation may be performed in
LTE-Advanced TDD or LTE-Advanced FDD systems.
DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1A is a graphical illustration of an uplink and
downlink subframe separated in the frequency domain for the FDD
mode.
[0005] FIG. 1B is a graphical illustration of uplink and downlink
subframes sharing a carrier frequency in the TDD mode.
[0006] FIG. 2 is a schematic representation of an example wireless
cellular communication system based on 3GPP long term evolution
(LTE).
[0007] FIG. 3 is a schematic block diagram illustrating an access
node device according to one embodiment.
[0008] FIG. 4 is a schematic block diagram illustrating a user
equipment device according to one embodiment.
[0009] FIG. 5 is a schematic diagram of a physical uplink control
channel format 1a/1b slot structure with normal cyclic prefix.
[0010] FIG. 6 is a schematic diagram showing an example physical
uplink control channel resource mapping scheme.
[0011] FIG. 7A is an example schematic diagram illustrating
downlink hybrid automatic repeat request timing linkages in
inter-band carrier aggregation with UL/DL configuration 6 on the
primary cell and UL/DL configuration 2 on the secondary cell.
[0012] FIG. 7B is an example schematic diagram illustrating
downlink hybrid automatic repeat request timing linkages in
inter-band carrier aggregation with UL/DL configuration 1 on the
primary cell and UL/DL configuration 4 on secondary cell.
[0013] FIG. 8 is a process flowchart for using an explicit PUCCH
resource mapping.
DETAILED DESCRIPTION
[0014] The present disclosure pertains to uplink control channel
resource collisions, and more particularly to physical uplink
control channel resource collision that may occur in systems using
carrier aggregation. Specific embodiments described herein relate
to physical uplink control channel (PUCCH) resources in a system
using inter-band carrier aggregation with different UL/DL TDD
configurations. In the various implementations described in this
disclosure, PUCCH resources may be used more effectively by
avoiding, preventing, detecting, resolving, or mitigating various
types of PUCCH resource collisions described herein.
[0015] Certain aspects of the systems, methods, and apparatuses are
part of a wireless communications network. Downlink (DL) hybrid
automatic repeat request (HARD) timing linkages associated with a
first component carrier and a second component carrier can be
determined, the first component carrier having a different uplink
(UL) and DL configuration than the second component carrier. A
derived downlink association set can be determined. A physical
uplink control channel (PUCCH) resource can be identified for the
second component carrier. An indicator of the PUCCH resource can be
sent to a user equipment.
[0016] In certain aspects, the PUCCH resource is indicated based,
at least in part, on at least one acknowledgement/negative
acknowledgement resource indicator (ARI) bit. The at least one ARI
bit is communicated with at least one transmit power control (TPC)
bit.
[0017] In certain aspects, the first component carrier comprises a
primary cell and the second component carrier comprises a secondary
cell.
[0018] Mobile electronic devices may operate in a communications
network, such as the network shown in FIG. 2, which is based on the
third generation partnership project (3GPP) long term evolution
(LTE), also known as Evolved Universal Terrestrial Radio Access
(E-UTRA). More specifically, FIG. 2 is a schematic representation
of an example wireless communication system 200 based on 3GPP LTE.
The system 200 shown in FIG. 2 includes a plurality of base
stations 212 (i.e., 212a and 212b). In the LTE example of FIG. 2,
the base stations are shown as evolved Node B (eNB) 212a,b. In this
disclosure, references to eNB are intended to refer to an access
node device, such as a base station or any other communications
network node that provides service to a mobile station including
femtocell, picocell, or the like. The example wireless
communication system 200 of FIG. 2 may include one or a plurality
of radio access networks 210, core networks (CNs) 220, and external
networks 230. In certain implementations, the radio access networks
may be Evolved Universal Mobile Telecommunications System (UMTS)
terrestrial radio access networks (EUTRANs). In addition, in
certain instances, core networks 220 may be evolved packet cores
(EPCs). Further, there may be one or more mobile electronic devices
202 obtaining communication services via the example wireless
communication system 200. In some implementations, 2G/3G systems
240, e.g., Global System for Mobile communication (GSM), Interim
Standard 95 (IS-95), Universal Mobile Telecommunications System
(UMTS) and CDMA2000 (Code Division Multiple Access) may also be
integrated into the communication system 200.
[0019] In the example LTE system shown in FIG. 2, the EUTRAN 210
includes eNB 212a and eNB 212b. Cell 214a is the service area of
eNB 212a and Cell 214b is the service area of eNB 212b. The term
cell is intended to describe a coverage area associated with a base
station regardless and may or may not overlap with the coverage
areas associated with other base stations. In FIG. 2, User
Equipment (UE) 202a and UE 202b operate in Cell 214a and are served
by eNB 212a. The EUTRAN 210 can include one or a plurality of eNBs
212 and one or a plurality of UEs can operate in a cell. The eNBs
212 communicate directly to the UEs 202. In some implementations,
the eNB 212 may be in a one-to-many relationship with the UE 202,
e.g., eNB 212a in the example LTE system 200 can serve multiple UEs
202 (i.e., UE 202a and UE 202b) within its coverage area Cell 214a,
but each of UE 202a and UE 202b may be connected only to one eNB
212a at a time. In some implementations, the eNB 212 may be in a
many-to-many relationship with the UEs 202, e.g., UE 202a and UE
202b can be connected to eNB 212a and eNB 212b. The eNB 212a may be
connected to eNB 212b with which handover may be conducted if one
or both of UE 202a and UE 202b travels from cell 214a to cell 214b.
UE 202 may be any communications device used by an end-user to
communicate, for example, within the LTE system 200. The UE 202 may
alternatively be referred to as mobile electronic device, user
equipment, user device, mobile device, mobile station, subscriber
station, or wireless terminal. In some embodiments, UE 202 may be a
cellular phone, personal data assistant (PDA), smart phone, laptop,
tablet personal computer (PC), pager, portable computer, or other
types of mobile communications device, including communications
apparatus used in wirelessly connected automobiles, appliances, or
clothing.
[0020] UEs 202 may transmit voice, video, multimedia, text, web
content and/or any other user/client-specific content. On the one
hand, the transmission of some of these contents, e.g., video and
web content, may require high channel throughput to satisfy the
end-user demand. On the other hand, the channel between UEs 202 and
eNBs 212 may be contaminated by multipath fading, due to the
multiple signal paths arising from many reflections in the wireless
environment. Accordingly, the UEs' transmission may adapt to the
wireless environment. In short, UEs 202 generate requests, send
responses or otherwise communicate in different means with Enhanced
Packet Core (EPC) 220 and/or Internet Protocol (IP) networks 230
through one or more eNBs 212.
[0021] A radio access network is part of a mobile telecommunication
system which implements a radio access technology, such as UMTS,
CDMA2000, and 3GPP LTE. In many applications, the Radio Access
Network (RAN) included in a LTE telecommunications system 200 is
called an EUTRAN 210. The EUTRAN 210 can be located between UEs 202
and EPC 220. The EUTRAN 210 includes at least one eNB 212. The eNB
can be a radio base station that may control all or at least some
radio related functions in a fixed part of the system. The at least
one eNB 212 can provide radio interface within their coverage area
or a cell for UEs 202 to communicate. eNBs 212 may be distributed
throughout the communications network to provide a wide area of
coverage. The eNB 212 directly communicates to one or a plurality
of UEs 202, other eNBs, and the EPC 220.
[0022] The eNB 212 may be the end point of the radio protocols
towards the UE 202 and may relay signals between the radio
connection and the connectivity towards the EPC 220. In certain
implementations, the EPC 220 is the main component of a core
network (CN). The CN can be a backbone network, which may be a
central part of the telecommunications system. The EPC 220 can
include a mobility management entity (MME), a serving gateway
(SGW), and a packet data network gateway (PGW). The MME may be the
main control element in the EPC 220 responsible for the
functionalities including the control plane functions related to
subscriber and session management. The SGW can serve as a local
mobility anchor, such that the packets are routed through this
point for intra EUTRAN 210 mobility and mobility with other legacy
2G/3G systems 240. The SGW functions may include the user plane
tunnel management and switching. The PGW may provide connectivity
to the services domain including external networks 230, such as the
IP networks. The UE 202, EUTRAN 210, and EPC 220 are sometimes
referred to as the evolved packet system (EPS). It is to be
understood that the architectural evolvement of the LTE system 200
is focused on the EPS. The functional evolution may include both
EPS and external networks 230.
[0023] Though described in terms of FIG. 2, the present disclosure
is not limited to such an environment. In general,
telecommunication systems may be described as communications
networks made up of a number of radio coverage areas, or cells that
are each served by a base station or other fixed transceiver.
Example telecommunication systems include Global System for Mobile
Communication (GSM) protocols, Universal Mobile Telecommunications
System (UMTS), 3GPP Long Term Evolution (LTE), and others. In
addition to telecommunication systems, wireless broadband
communication systems may also be suitable for the various
implementations described in the present disclosure. Example
wireless broadband communication systems include IEEE 802.11
wireless local area network, IEEE 802.16 WiMAX network, etc.
[0024] Referring to FIG. 3, an access node device (for example, eNB
212a in FIG. 2) according to one embodiment will be described
below. The illustrated device 300 includes a processing module 302,
a wired communication subsystem 304, and a wireless communication
subsystem 306. The processing module 302 can include a processing
component (alternatively referred to as "processor" or "central
processing unit (CPU)") capable of executing instructions related
to one or more of the processes, steps, or actions described above
in connection with one or more of the embodiments disclosed herein.
The processing module 302 can also include other auxiliary
components, such as random access memory (RAM), read only memory
(ROM), secondary storage (for example, a hard disk drive or flash
memory). The processing module 302 can execute certain instructions
and commands to provide wireless or wired communication, using the
wired communication subsystem 304 or the wireless communication
subsystem 306. A skilled artisan will readily appreciate that
various other components can also be included in the device
300.
[0025] FIG. 4 is a schematic block diagram illustrating a user
equipment device (for example, UEs 202a, 202b in FIG. 2) according
to one embodiment. The illustrated device 400 includes a processing
unit 402, a computer readable storage medium 404 (for example, ROM
or flash memory), a wireless communication subsystem 406, a user
interface 408, and an I/O interface 410.
[0026] Similar to the processing module 302 of FIG. 3, the
processing unit 402 can include a processing component configured
to execute instructions related to one or more of the processes,
steps, or actions described above in connection with one or more of
the embodiments disclosed herein. The processing unit 402 can also
include other auxiliary components, such as random access memory
(RAM) and read only memory (ROM). The computer readable storage
medium 404 can store an operating system (OS) of the device 400 and
various other computer executable software programs for performing
one or more of the processes, steps, or actions described
above.
[0027] The wireless communication subsystem 406 is configured to
provide wireless communication for data and/or control information
provided by the processing unit 402. The wireless communication
subsystem 406 can include, for example, one or more antennas, a
receiver, a transmitter, a local oscillator, a mixer, and a digital
processing (DSP) unit. In some embodiments, the wireless
communication subsystem 406 can support a multiple input multiple
output (MIMO) protocol.
[0028] The user interface 408 can include, for example, a screen or
touch screen (for example, a liquid crystal display (LCD), a light
emitting display (LED), an organic light emitting display (OLED), a
microelectromechanical system (MEMS) display), a keyboard or
keypad, a trackball, a speaker, or a microphone. The I/O interface
410 can include, for example, a universal serial bus (USB)
interface. A skilled artisan will readily appreciate that various
other components can also be included in the device 400.
[0029] In the 3GPP LTE TDD system, a subframe of a radio frame can
be a downlink, an uplink or a special subframe (the special
subframe includes downlink and uplink time regions separated by a
guard period for downlink to uplink switching). Currently, there
are seven different UL/DL configuration schemes that may be used in
LTE TDD operations, as shown in Table 1 below. Table 1 shows LTE
TDD Uplink-Downlink Configurations. D represents downlink
subframes, U represents uplink subframes and S represents special
subframes. In each special subframe S, there are three parts which
are: i) the downlink pilot time slot (DwPTS), ii) the guard period
(GP) and iii) the uplink pilot time slot (UpPTS). Downlink
transmissions on the physical downlink shared channel (PDSCH) may
be made in DL subframes or in the DwPTS portion of a special
subframe. Uplink transmissions on the physical uplink control
channel (PUCCH) or physical uplink shared channel (PUSCH) may only
be made in UL subframes, since the UpPTS portion of a special
subframe is too short to accommodate these channels.
TABLE-US-00001 TABLE 1 LTE TDD Uplink-Downlink Configurations
Uplink-downlink Downlink-to-Uplink Subframe number configuration
Switch-point periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U
U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D
S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D
D D D 6 5 ms D S U U U D S U U D
[0030] As shown in Table 1, there are two switch point
periodicities specified in the LTE standard, 5 ms and 10 ms. 5 ms
switch point periodicity is introduced to support the co-existence
between LTE and low chip rate UTRA TDD systems, and 10 ms switch
point periodicity is for the coexistence between LTE and high chip
rate UTRA TDD systems. The supported configurations cover a wide
range of UL/DL allocations from "DL heavy" 1:9 ratio to "UL heavy"
3:2 ratio. (The DL allocations in these ratios include both DL
subframes and special subframes (which can also carry downlink
transmissions in DwPTS).) Therefore, compared to FDD, TDD systems
have more flexibility in terms of the proportion of resources
assignable to uplink and downlink communications within a given
amount of spectrum. Specifically, it is possible to unevenly
distribute the radio resources between uplink and downlink. This
will provide a way to utilize the radio resources more efficiently
by selecting an appropriate UL/DL configuration based on
interference situation and different traffic characteristics in DL
and UL.
[0031] As understood to persons of skill in the art, UL (or DL)
transmissions do not occur in every subframe in an LTE TDD system.
Since the UL and DL transmissions are not continuous, scheduling
and hybrid automatic repeat request (HARQ) timing relationships for
an LTE TDD system are defined in the specifications. Currently, the
HARQ ACK/NACK timing relationship for downlink is defined in Table
2 below. Table 2 may be used to show which uplink subframes should
carry uplink HARQ ACK/NACK transmissions associated with M multiple
downlink subframes. Table 2 shows downlink association set index K:
{k.sub.0, k.sub.1, . . . k.sub.M-1}. It associates an UL sub-frame
n, which conveys ACK/NACK, with DL sub-frames n-k.sub.i, i=0 to
M-1.
TABLE-US-00002 TABLE 2 Downlink Association Set Index K: {k.sub.0,
k.sub.1, . . . k.sub.M-1} UL-DL Subframe n Configuration 0 1 2 3 4
5 6 7 8 9 0 -- -- 6 -- 4 -- -- 6 -- 4 1 -- -- 7, 6 4 -- -- -- 7, 6
4 -- 2 -- -- 8, 7, 4, 6 -- -- -- -- 8, 7, 4, 6 -- -- 3 -- -- 7, 6,
11 6, 5 5, 4 -- -- -- -- -- 4 -- -- 12, 8, 7, 11 6, 5, 4, 7 -- --
-- -- -- -- 5 -- -- 13, 12, 9, 8, 7, 5, 4, 11, 6 -- -- -- -- -- --
-- 6 -- -- 7 7 5 -- -- 7 7 --
[0032] As an illustrative example, when using TDD UL/DL
configuration 6, there are uplink subframes that occur in subframes
2, 3, 4, 7, and 8. (see also UL/DL configuration 6 in Table 1).
Referring to Table 2, for the UL/DL configuration 6, at subframe 2,
the downlink association set index K: {k.sub.0, k.sub.1, . . .
k.sub.M-1} can be represented as K:{7}.
[0033] The uplink HARQ ACK/NACK timing linkage is shown in Table 3
below. As understood to a person of skill in the art, a timing
linkage represents a relationship between when downlink data is
transmitted in downlink subframes and when corresponding HARQ
ACK/NACK feedback is transmitted in one or more subsequent uplink
subframes. Table 3 shows k values for HARQ ACK/NACK. It indicates
that the physical hybrid ARQ indicator channel (PHICH) ACK/NACK
received in DL sub-frame i is linked with the UL data transmission
in UL sub-frame i-k, k is given in Table 3. In addition, for UL/DL
configuration 0, in sub-frames 0 and 5, when I.sub.PHICH=1, k=6.
This is because there may be two ACK/NACKs for a UE transmitted on
the PHICH in subframes 0 and 5.
TABLE-US-00003 TABLE 3 k for HARQ ACK/NACK TDD UL/DL subframe
number i Configuration 0 1 2 3 4 5 6 7 8 9 0 7 4 7 4 1 4 6 4 6 2 6
6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6
[0034] The UL grant, ACK/NACK and transmission/retransmission
relationship is in Table 4 below. Table 4 shows k values for
physical uplink shared channel (PUSCH) transmission. The UE shall
upon detection of a physical downlink control channel (PDCCH) with
DCI format 0 and/or a PHICH transmission in sub-frame n intended
for the UE, adjust the corresponding PUSCH transmission in
sub-frame n+k, with k given in Table 4.
[0035] For TDD UL/DL configuration 0, if the LSB of the UL index in
the DCI format 0 is set to 1 in sub-frame n or a PHICH is received
in sub-frame n=0 or 5 in the resource corresponding to
I.sub.PHICH=1, or PHICH is received in sub-frame n=1 or 6, the UE
shall adjust the corresponding PUSCH transmission in sub-frame n+7.
If, for TDD UL/DL configuration 0, both the most significant bit
(MSB) and least significant bit (LSB) of the UL index field in the
DCI format 0 are set in sub-frame n, the UE shall adjust the
corresponding PUSCH transmission in both sub-frames n+k and n+7,
with k given in Table 4.
TABLE-US-00004 TABLE 4 k for PUSCH transmission TDD UL/DL subframe
number n Configuration 0 1 2 3 4 5 6 7 8 9 0 4 6 4 6 1 6 4 6 4 2 4
4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5
[0036] Both grant and HARQ timing linkage in TDD are more
complicated than the fixed time linkages used in an LTE FDD
system.
[0037] The physical uplink control channel (PUCCH) format 1a/1b may
be used to transmit the ACK/NACK signalling (when ACK/NACK is not
multiplexed into a PUSCH transmission). The slot structure of PUCCH
formats 1a and 1b with normal cyclic prefix is shown in FIG. 5.
FIG. 5 is a schematic diagram of a physical uplink control channel
format 1a/1b slot structure with normal cyclic prefix. Each format
1a/1b PUCCH is in a subframe made up of two slots. The same
modulation symbol is used in both slots. Without channel selection,
formats 1a and 1b carry one and two ACK/NACK bits, respectively.
These bits are encoded into the modulation symbol using either BPSK
or QPSK modulation based on the number of ACK/NACK bits. The symbol
is multiplied by a cyclic-shifted sequence with length-12. Then,
the samples are mapped to the 12 subcarriers which the PUCCH is to
occupy and then converted to the time domain via an IDFT. The
spread signal is then multiplied with an orthogonal cover sequence
with the length of 4, w(m), where m.epsilon.{0,1,2,3} corresponds
to each one of 4 data bearing symbols in the slot. There are three
reference symbols in each slot (located in the middle symbols of
the slot) that allow channel estimation for coherent demodulation
of formats 1a/1b.
[0038] Similar to FDD, for TDD, the PUCCH resource which a UE is to
use may be signalled via either implicit or explicit signaling.
[0039] In the case of implicit signaling, for a PDSCH transmission
indicated by the detection of corresponding PDCCH or a PDCCH
indicating downlink SPS release in sub-frame n-k.sub.i where
k.sub.i.epsilon.K defined in Table 2, the PUCCH resource
n.sub.PUCCH,i.sup.(1)=(M-i-1)N.sub.c+iN.sub.c+1+n.sub.CCE,i+N.sub.PUCCH.s-
up.(1), where c is selected from {0, 1, 2, 3} such that
N.sub.c.ltoreq.n.sub.CCE,i<N.sub.c+1, where M is the number of
elements in the set K defined in Table 2. N.sub.c=max{0,.left
brkt-bot.[N.sub.RB.sup.DL(N.sub.sc.sup.RBc-4)]/36.right brkt-bot.},
n.sub.CCE,i is the number of the first control channel element
(CCE) used for transmission of the corresponding PDCCH in subframe
n-k.sub.i, and N.sub.PUCCH.sup.(1) is configured by higher
layers.
[0040] In the case of explicit signalling, the PUCCH resource may
be indicated via the ACK/NACK resource indicator (ARI) bits and/or
higher layer configuration. FIG. 6 illustrates the PUCCH resource
mapping scheme. FIG. 6 is a schematic diagram showing an example
physical uplink control channel resource mapping scheme. In carrier
aggregation (CA), PUCCH resources may be signalled implicitly using
the location of the scheduling grant for the UE on the PDCCH of its
primary cell (PCell). PUCCH resources may also be explicitly
indicated using the ARI bits contained in the grant for the UE on
the PDCCH of one of the UE's secondary cells (SCells). In some
implementations, resources of the SCell may be cross carrier
scheduled by the PCell. For example, a PDCCH transmitted on PCell
may provide scheduling for a PDSCH on SCell. In cross carrier
scheduling, the PUCCH resource allocated to a UE may be implicitly
signalled by the first CCE index of the PDCCH. In other
implementations, the SCell is separate-scheduled by PDCCH on SCell
itself (i.e. a PDCCH on SCell refers to a PDSCH grant also on
SCell), and the PUCCH resource index is determined by the ARI bits
in the grant transmitted on the SCell PDCCH.
[0041] LTE-Advanced Release-10 currently only supports CA when
using the same UL/DL configuration on all the aggregated carriers.
Inter-band carrier aggregation with different TDD UL/DL
configurations on the carriers from different bands may facilitate
the bandwidth flexibility and coexistence with legacy TDD
systems.
[0042] It is noted that a component carrier (CC) is also known as a
serving cell or a cell. Furthermore, when multiple CCs are
scheduled, for each UE, one of the CCs can be designated as a
primary carrier which is used for PUCCH transmission,
semi-persistent scheduling, etc., while the remaining one or more
CCs are configured as secondary CCs. This primary carrier is also
known as primary cell (PCell), while the secondary CC is known as
secondary cell (SCell).
[0043] The timing linkage complexity in TDD systems increases,
especially in view of CA with different TDD configurations, because
with different TDD configurations, there are time instances with
direction conflicting subframes among aggregated CCs (e.g. an UL
subframe on CC1 at the same time as CC2 has a DL subframe). Also
the timing linkage is different for each different TDD
configuration and, furthermore, certain control signals have to be
on a specific carrier, e.g. PUCCH has to be on PCell, etc. This may
lead to a much greater control channel resource collision
possibility in some scenarios.
[0044] Because PUCCH is transmitted on PCell in the case of
inter-band CA with different UL/DL configurations, it increases the
possibility of PUCCH resource collision. Described in this
disclosure are two types of PUCCH resource collision. One type is
that collision takes place between different UEs when ACK/NACKs
from different UEs happen to use the same PUCCH resource, which may
be referred to as a Type 1 collision or an inter-UE collision.
Another type of collision occurs within the same UE when the PUCCH
format 1a/1b resources from PCell and SCell are mapped onto the
same PUCCH resource: this type of collision may be referred to as a
Type 2 collision or an intra-UE collision. We consider both
scenarios in this disclosure.
[0045] FIG. 7A is an example schematic diagram illustrating
downlink hybrid automatic repeat request (HARQ) timing linkages in
inter-band carrier aggregation. In FIG. 7A, a primary cell (PCell)
is utilizing UL/DL configuration 6 and a secondary cell (SCell) is
utilizing UL/DL configuration 2. In the example scenario shown in
FIG. 7A, two TDD carriers are aggregated, and the PCell 702 is set
as UL/DL configuration 6 and SCell 704 is with UL/DL configuration
2, in full duplex mode. PCell 702 follows its own DL HARQ timing
relationship, which is UL/DL configuration 6, and SCell 704 DL HARQ
follows the timing of UL/DL configuration 2. The PCell 702 is shown
with PDCCH configuration 706 and PUCCH configuration 708; SCell 704
is shown with PDCCH configuration 712 (PDCCH may or may not be
configured on SCell). The arrows 710 represent the DL HARQ timing
for a first (e.g., non-CA legacy) UE served by PCell 702; while the
arrows 716 represent the DL HARQ timing of SCell 704 for a second
(e.g., CA) UE. A non-CA legacy UE on the carrier with UL/DL
configuration 6 will follow the original Rel. 8/9/10 timing linkage
of UL/DL configuration 6.
[0046] For legacy UEs on PCell PUCCH resource is determined by the
first CCE for subframe 0 grant; while for CA UEs SCell PUCCH
resources are based on four different subframes.
[0047] Turning to the PUCCH format 1a/1b resource at subframe #7
720 in FIG. 7A, for a legacy non-CA UE whose serving cell has UL/DL
configuration 6, the PUCCH resource is determined by the first CCE
index for transmission of the corresponding PDCCH in subframe #0 as
described above. For a CA UE, it may require four PUCCH resources
at subframe #7 720 for ACK/NACKs from four different PDSCH
subframes, #9, #0, #1 and #3. In the case of cross carrier
scheduling, these PUCCH resources are determined by the same
fashion as described above, but the CCE indexes used in the
calculation are from the different subframes for transmission of
the corresponding PDCCHs. Therefore, it may result in the same
PUCCH channel resource index for the non-CA UE and the CA UE at the
same UL subframe.
[0048] FIG. 7B is an example schematic 750 diagram illustrating DL
HARQ timing linkages in inter-band carrier aggregation with UL/DL
configuration 1 on the PCell 752 and UL/DL configuration 4 on SCell
754. PCell 752 follows its own DL HARQ timing relationship, which
is UL/DL configuration 1, and SCell 754 DL HARQ follows the timing
of UL/DL configuration 4. The arrows 760 represent the DL HARQ
timing of PCell 752, the arrows 766 represent the DL HARQ timing of
SCell 754. PCell 752 includes PDCCH configuration 756 and PUCCH
configuration 758. SCell 754 includes PDCCH configuration 762.
[0049] As shown in FIG. 7B, for cross carrier scheduling, the PUCCH
format 1a/1b resources at subframes #2 are determined by the first
CCE index for transmission of the corresponding PDCCH in subframes
#5 and #6 of PCell 752 and subframes #0, #1, #4, #5 of SCell 754.
Therefore, it may result in PUCCH resource collision between PCell
752 and SCell 754 within the CA UE at subframe 2. It should be
understood that the PUCCH channel index mapped from different
subframes may have the same number. In FIG. 7B, a potential PUCCH
resource collision may also occur in subframe 3.
[0050] In one aspect of the present disclosure include, an
algorithm can be used to determine PUCCH format 1a/1b resource
mapping. The algorithm may be used throughout the system, or may be
selectively used in the case of inter-band CA with different TDD
UL/DL configurations. Because PUCCH is transmitted only on a single
cell (PCell), we have to design a single PUCCH resource mapping
rule which can be applied to all component carriers in CA.
[0051] In Table 2 above, each entry represents the downlink
association set index K at a subframe n for a given UL/DL
configuration. For convenience in expression, two additional
indexes can be assigned to K: K.sub.j,n, with n indicating subframe
number in a frame (from 0 to 9) and j representing UL/DL
configuration (from 0 to 6). For example, K.sub.1,2 refers to the
subframe 2 of a carrier using UL/DL configuration 1. Referring to
the information of Table 2, the following expression should be
understood as representing the downlink association set index K
associated for UL/DL configuration 1, subframe 2: K.sub.1,2={7,6}.
Similarly, the downlink association set index K for UL/DL
configuration 2, subframe 2 is represented by the expression
K.sub.2,2={8,7,4,6}. The downlink association set is null at any DL
or special subframe.
[0052] A CA UE can use the currently existing Rel 8/9/10 PUCCH
mapping rule for the PCell PDSCH ACK/NACK. The non-CA UE served by
the PCell follows the existing mapping rule as well. Therefore, no
collision will occur. For SCell PDSCH ACK/NACK, if using different
DL HARQ timing than PCell, an explicit signalling can be used to
directly indicate the PUCCH resource to the UE. In certain
implementation, the ACK/NACK Resource Indicator (ARI) bit(s) can be
used to convey the exact location of PUCCH resource as is done for
separate scheduling case in Rel 10. Table 5 below shows the
correspondence between Transmit Power Control (TPC) bits (used as
ARI bits) and PUCCH resource. Two TPC bits are contained in all
UE-specific Downlink Control Information (DCI) formats which are
signalled on the PDCCH to indicate downlink (PDSCH) and uplink
(PUSCH) grants to a UE. These TPC bits are normally used to perform
uplink power control for PUCCH and PUSCH transmissions. However,
when carrier aggregation is used, it may not be necessary to use
the TPC bits in all signalled DCIs for power control purposes, and
hence it is possible to reuse one or both of these TPC bits for
other purposes when they are not required for power control. Table
5 shows PUCCH resource values for HARQ ACK Resource for PUCCH.
TABLE-US-00005 TABLE 5 PUCCH Resource Value for HARQ-ACK Resource
for PUCCH Value of `TPC command for n.sub.PUCCH,j.sup.(1) or PUCCH`
(n.sub.PUCCH,j.sup.(1), n.sub.PUCCH,j+1.sup.(1)) `00` The 1st PUCCH
resource value configured by the higher layers `01` The 2.sup.nd
PUCCH resource value configured by the higher layers `10` The
3.sup.rd PUCCH resource value configured by the higher layers `11`
The 4.sup.th PUCCH resource value configured by the higher
layers
[0053] FIG. 8 is a process flowchart 800 for using an explicit
PUCCH resource mapping. The DL HARQ timing linkage can be
determined (802). Depending on the combination of TDD UL/DL
configurations for CCs (i.e., timing rules) (804), a single PUCCH
mapping rule may work for ACK/NACKs of both PCell and SCell (808).
However, other times, the explicit resource mapping is used (806).
For example, when multiple timing rules exist for CA UEs, the PCell
may still use the implicit PUCCH mapping rules, consistent with
Rel10; for SCell, an explicit PUCCH resource mapping can be used
(806).
[0054] FIG. 8 above describes a method executed in a base station
in a wireless communications network that utilizes explicit
signalling. The base station can determine a downlink (DL) hybrid
automatic repeat request (HARQ) timing for a first component
carrier and a second component carrier. The first component carrier
may have a different DL HARQ timing configuration than the second
component carrier. The first component carrier may be a primary
cell (PCell) and the second component carrier may be a secondary
cell (SCell). A physical uplink control channel (PUCCH) resource
for the second component carrier can be identified, e.g.,
explicitly. The explicit identification of the PUCCH resource can
be associated with (or represented by) a resource indicator. The
base station can send the resource indicator of the PUCCH resource
to a user equipment. The PUCCH resource may be identified based, at
least in part, on at least one acknowledgement/negative
acknowledgement resource indicator (ARI) bit. The at least one ARI
bit may be communicated with at least one transmit power control
(TPC) bit. The term "identified" is meant to capture different
functional aspects, such as choosing, selecting, receiving an
indication of, determining, calculating, mapping, etc.
[0055] While several embodiments have been provided in the present
disclosure, it should be understood that the disclosed systems and
methods may be embodied in many other specific forms without
departing from the scope of the present disclosure. The present
examples are to be considered as illustrative and not restrictive,
and the intention is not to be limited to the details given herein.
For example, the various elements or components may be combined or
integrated in another system or certain features may be omitted, or
not implemented.
[0056] Also, techniques, systems, subsystems and methods described
and illustrated in the various embodiments as discrete or separate
may be combined or integrated with other systems, modules,
techniques, or methods without departing from the scope of the
present disclosure. Other items shown or discussed as coupled or
directly coupled or communicating with each other may be indirectly
coupled or communicating through some interface, device, or
intermediate component, whether electrically, mechanically, or
otherwise. Other examples of changes, substitutions, and
alterations are ascertainable by one skilled in the art and could
be made without departing from the spirit and scope disclosed
herein.
[0057] While the above detailed description has shown, described,
and pointed out the fundamental novel features of the invention as
applied to various embodiments, it will be understood that various
omissions and substitutions and changes in the form and details of
the system illustrated may be made by those skilled in the art,
without departing from the intent of the disclosure.
* * * * *